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Thread: Where and how to get ISA format PCBs made

  1. #1

    Default Where and how to get ISA format PCBs made

    Hi All,

    I've been looking into where to get some ISA form factor PCBs made. The only PCB place I have used before is jlcpcb and I had good results for that project but no edge connectors were involved. The information on their website on bevelling edge connectors is ambiguous and while they have been very quick to reply to email questions its clear the guy I've been talking to is struggling to understand my questions, language barrier I suspect. They also don't offer hard gold as an option at least within the automated order system.

    The old ISA boards I have all seem to bevel at about a 45 degree angle and the pads run right up to the bevel. On most of them it looks like the pad was initially longer and has been shortened during the bevelling process. I'm concluding this because you can see a bit of a slope on the end of the pads and in some cases a very thin bit of exposed copper. The bevel seems to typically start about 0.5mm from the edge.

    jlcpcb tell you:
    For the finger required to be 45 bevelled, enough space should be left between the finger to the board edge to prevent fingers being cut, please refer to the safe space as following for different board thickness
    1555753147565033312.png

    Its neither clear to me how the bevelling will get to a pad more than about 0.8mm in (with T reduced to zero), nor if they are saying the pad will be neatly cut back if it overlaps the bevel or if things will be ripped off further back.

    All these factors are just not giving me the confidence to commit to ordering at the moment. I was curious to know who other people are using? What's the general view on the importance of hard gold on edge connectors, its what should really be used as lead free HASL (99% tin) isn't ideal as mixing tin and gold contacts is definitely not recommended engineering. ENIG is wafer thin and the gold won't last more than a few insertions I suspect. Then its a gold on nickel contact which I would imagine is also bad, mixed contacts tends to cause increased corrosion and or metal migration over time. Lead HASL would prevent me from being able to sell the left over boards, assuming the design even works. In the UK you can't sell new stuff with lead in it.

    Anyone have any practical experience of the real world durability of ENIG on edge connectors? Is it worth paying for the slightly thicker gold layer some vendor sell?

    On boards other people are selling most of them seem to be ENIG or HASL. One obvious exception being the Glitch Works XT-IDE board, somehow he was able to sell those at $10 each! I've not found anywhere that gets the price that low unless you are making far more than I can afford. Hard gold and small quantities is just too expensive.

    Also does anyone know what sort of gold plating was used back when ISA cards were still the norm? The plating seems to look much better on newer PCI cards and the shape of the contact strongly hints the tips of the pads originally continued to the edge of the PCB to facilitate electroplating.

    Thanks,

    Andy

  2. #2
    Join Date
    Sep 2006
    Location
    Silicon Valley
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    2,149

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    Quote Originally Posted by Andy Mitchell View Post
    One obvious exception being the Glitch Works XT-IDE board, somehow he was able to sell those at $10 each! I've not found anywhere that gets the price that low unless you are making far more than I can afford. Hard gold and small quantities is just too expensive.
    I'm curious about this as well. Glitch's XT-IDE boards are MUCH better than the competitions

  3. #3

    Default

    I got a run of ISA prototype cards from JLCPCB in ENIG with beveled edge. The beveling came out great, I just selected the "gold fingers" option on the ordering screen. ENIG sucks and I would have only used hard gold if these were for a production/sale run but it's (ENIG) still legions better than HASL. After about 20-50 insertions I've seen some slight surface abrasion on one of my protos but most of the coating is still there.

    There is a shop that does hard gold at a reasonable surcharge for small runs, but it's still going to be at least a $75 premium, so I still recommend ENIG for your prototypes. The vast majority of factory produced ISA cards I examined are hard gold. You'll see the occasional tin plated one that's some super cheap rinky dink crap.

    PS I have kicad design files of my ISA edge connector that I'd be willing to share if you're interested. I measured a couple dozen cards to get the physical dimensions of the card edge just right. They fit great and the beveling makes insertion nice and smooth.

  4. #4

    Default

    Quote Originally Posted by maxtherabbit View Post
    I got a run of ISA prototype cards from JLCPCB in ENIG with beveled edge. The beveling came out great, I just selected the "gold fingers" option on the ordering screen. ENIG sucks and I would have only used hard gold if these were for a production/sale run but it's (ENIG) still legions better than HASL. After about 20-50 insertions I've seen some slight surface abrasion on one of my protos but most of the coating is still there.

    There is a shop that does hard gold at a reasonable surcharge for small runs, but it's still going to be at least a $75 premium, so I still recommend ENIG for your prototypes. The vast majority of factory produced ISA cards I examined are hard gold. You'll see the occasional tin plated one that's some super cheap rinky dink crap.

    PS I have kicad design files of my ISA edge connector that I'd be willing to share if you're interested. I measured a couple dozen cards to get the physical dimensions of the card edge just right. They fit great and the beveling makes insertion nice and smooth.
    Thanks for the info, very helpful. It would be useful to have a look at your Kicad files as whatever you did should work again.

  5. #5

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    Quote Originally Posted by Andy Mitchell View Post
    Thanks for the info, very helpful. It would be useful to have a look at your Kicad files as whatever you did should work again.
    ISA edge.zip

  6. #6
    Join Date
    Dec 2019
    Location
    Sydney, Australia
    Posts
    19

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    Elecrow can do hard gold (I'm not sure about prices):
    https://www.elecrow.com/premium-pcb-service-p-1061.html


    You might be interested in reading these to:
    https://www.eevblog.com/forum/manufa...gold-fingers)/
    https://www.eurocircuits.com/blog/go...ge-connectors/



    Some other PCB related links people might be interested in:

    PCB Shopper (PCB price comparison website, but JLC PCB is almost always cheapest these days):
    https://pcbshopper.com/

    The EEVBlog also has a good list of PCB manufacturers:
    https://www.eevblog.com/wiki/index.p..._Manufacturers

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